My invention relates to an installation for thermal treatment of container-packed commodities, such as foodstuffs or medicines, which containers are advanced groupwise in carriers, the installation having a conveying system for these carriers, at least one treatment space with an inlet and an outlet, and internal means for moving the carriers stepwise in a vertical direction within this treatment space. Such an installation is known per se in various embodiments; the treatment path therein extends substantially in a horizontal direction owing to which the apparatus gets considerable dimensions. Moreover notable forces are required for periodically displacing the carriers as the driving means should simultaneously push a plurality of carriers over a rather substantial horizontal distance.